Dispelling Myths About EQ

[DrWho]

The EV Dx38 does time-alignment, but it does not have seperate phase control. Roy makes an interesting point that you can compensate for phase by shifting the time alignment within the period of the crossover frequency...so basically you have +-180 degrees of phase rotation available through the delay knob without screwing up the time alignment of the system. In other words, a phase control would be accomplishing the same thing that a delay would be doing (or basically, a phase control IS a delay control).

[Travis In Austin]

The EV Dx38 does time-alignment, but it does not have seperate phase control. Roy makes an interesting point that you can compensate for phase by shifting the time alignment within the period of the crossover frequency...so basically you have +-180 degrees of phase rotation available through the delay knob without screwing up the time alignment of the system. In other words, a phase control would be accomplishing the same thing that a delay would be doing (or basically, a phase control IS a delay control).

Doc and Mark,

I'm with Coyotee-O on this, what in the heck does all of this mean in lay terms. Does it mean you should not use EQ even if it sound better? Does it mean if EQ sounds better you are an idiot. Does it mean that people who make EQ's are in a conpiracy with the people who make audio cables? Or, does it mean that if you don't have an EQ you are missing out on a lot of stuff? Or does it mean that if you had an EQ you could be listening a whole lot better?

Travis

[Coytee]

I'm with Coyotee-O on this, what in the heck does all of this mean in lay terms. Does it mean you should not use EQ even if it sound better? Does it mean if EQ sounds better you are an idiot. Does it mean that people who make EQ's are in a conpiracy with the people who make audio cables? Or, does it mean that if you don't have an EQ you are missing out on a lot of stuff? Or does it mean that if you had an EQ you could be listening a whole lot better?

Travis... I'm beginning to think that there is a conspiracy and it really means those who make the planes are in cahoots with those who make the conveyor belts....thereby forcing us all to buy automobiles since our personal planes are confused about whether or not they'd take off.....

[ap]..............

[au]..............

[:^)]

[mark1101]

The EV Dx38 does time-alignment, but it does not have seperate phase control. Roy makes an interesting point that you can compensate for phase by shifting the time alignment within the period of the crossover frequency...so basically you have +-180 degrees of phase rotation available through the delay knob without screwing up the time alignment of the system. In other words, a phase control would be accomplishing the same thing that a delay would be doing (or basically, a phase control IS a delay control).

Doc,

You are right about the EV and delay methods. I should have said "polarity" switch.

[sfogg]

Mark,

"Did you mention that your EV DX-38 also does time alignment of outputs and phase shifitng besides para EQ and active crossing?"

I don't have the DX-38, I use the DCX2496s. They have a phase control in addition to the delay, parametric EQ and the crossovers.

Shawn

[Coytee]

Not sure if this answers anyones question or not but the Dx38 DOES have a polarity switch. It can be set to normal or inverted.

[JohnA]

Jumping away from trying to redefine a parametric EQ as not being an EQ I see....

"Changing

the slope and the overlap of two significantly mis-aligned non-minimum

phase does not correct comb filtering or polar lobing."

Make up your mind.... seriously..... literally the post before this one you posted....

"Your insight regarding steeper slopes began as a given solution in the article."

Flip flop... flip flop....

"Yup! Just like them other ignort folks that you know more than! And you still fail to grasp this."

Did you read what I questioned you on? ........

Shawn

Shawn,

You

realize this is akin to arguing physics with a Star Trek Science

Officer. You get lots of techno-babble and no substance.

"Non-minimum phase" has no real definition or meaning. Perhaps if

the discussion was built around "phase shift (phase differences) of

less than 30 degrees at the listening position", there would be some

meaningful discussion. But, it's not. Is non-minimum phase

really maximum phase difference? Is maximum phase difference

defined as 90, 180, or 742 degrees? What frequencies are

involved? The original premise that EQ can degrade the sound of a

good system and cannot improve a bad system, if not used carefully, is

stupid simple and obvious. Worse yet, mas is lecturing to us,

with condescension, for no reason. Only a few of us use EQ or

tone controls in the home. I DO use them in my amateur sound

reinforcement work, to good advantage, but I recognize the results may

not be as beneficial at all points in the auditorium.

When you mud wrestle with a pig, you both get dirty but the pig likes it!

[mas]

Real quickly, as today has turned into a @#$%.

In delay units there are two methods of delay. (...and not that signal synchronization is trivial, its not! But let's pretend for a minute that it is. You may quickly begin to see a budding problem!)

The first case is easy.

Actual signal delay indicates the actual time/distance between the physical offsets of the acoustic origins.(e.g., 1ms - 1.13 ft). Such a unit requires more sophisticated design. Many such units provide signal delays of up to 10 ms or more. Buying a quality unit with such a calibrated function also usually indicates that the other functionality is up to snuff as well.

The other is the amorphous "phase delay", which is akin to putting a speedometer on a car and not labelling the scale with units.

Oh no, I can hear you saying it now! How can he say that!?

We are dealing with a fundamentally broadband unit. We can measure the acoustic origin via the impulse respulse with great accuracy. We can even ascertain the degree of astigmatism in a horn.

So let's see, what do we have. Well, to begin with, lots of questions and uncertainty. This should tell you why many of the cheaper units have a phase control and do not provide a calibrated signal delay. And it goes further, as each manufacturer can implement this system in any manner they choose, as it is not referenced to actual time and distance.

For you see, to say that you have , say +-180 degrees of phase adjustment says little. +-180 degrees relative to what? As phase is frequency dependent, which frequency do you select? If you are trying to align a broad passband device, what in heck does this mean? The fact is you cannot tell. And if the unit's phase control is referenced to a particular frequency, what does that mean if your passband of interest is in another part of the spectrum?

And suppose that you can measure the impulse response offsets of the two drivers' signals. Assuming that the unit is effective at all, is say, 180 degrees sufficient to align two signals? Remember, 360 degrees is one cycle. Are large physical offsets such as are typical with large offset style old school horns - such as the Heritage series, only a function of less than ONE cycle for signal synchronization?

The fundamental problem is that you are left with lots of questions and few answers. You have a control that is basically labeled "change". And you have a speedometer that has numbers, but you have no idea as to exactly what the numbers correspond.

Confused? Well, if you are relying simply on a "phase control", you should be. There is a reason that it pays to evaluate units prior to purchase. Not all are the same.

If you want a signal synchronization and an effective signal delay function, start looking for a unit that provides an accurate calibrated time offset.

Oh, and then you will want to be aware of the insertion delay of the unit. The amount of latency created by both inserting the unit into the signal path and the delay caused by the processing time of the unit itself.

If anyone likes, I can post some measured comparisons of quite a few of the currently available DSP.units. You will note quite a discrepancy among the various units.

You see, there is a bit more to this than simply reading the labelling on the knobs or fancy LCD screen or upon the computer screen, depending upon the provided interface.

Ain't audio fun? And you wonder why Bose and all of the other manufacturers of magic 'our boxes tune your room' systems are so successful selling systems where everything is 'taken care of' (or at least the brochure assures you that it has). And the more it costs, the better it must be! Right!? It sure beats thinking!

[mas]

Jumping away from trying to redefine a parametric EQ as not being an EQ I see....

"Changing

the slope and the overlap of two significantly mis-aligned non-minimum

phase does not correct comb filtering or polar lobing."

Make up your mind.... seriously..... literally the post before this one you posted....

"Your insight regarding steeper slopes began as a given solution in the article."

Flip flop... flip flop....

"Yup! Just like them other ignort folks that you know more than! And you still fail to grasp this."

Did you read what I questioned you on? ........

Shawn

Shawn,

You

realize this is akin to arguing physics with a Star Trek Science

Officer. You get lots of techno-babble and no substance.

"Non-minimum phase" has no real definition or meaning. Perhaps if

the discussion was built around "phase shift (phase differences) of

less than 30 degrees at the listening position", there would be some

meaningful discussion. But, it's not. Is non-minimum phase

really maximum phase difference? Is maximum phase difference

defined as 90, 180, or 742 degrees? What frequencies are

involved? The original premise that EQ can degrade the sound of a

good system and cannot improve a bad system, if not used carefully, is

stupid simple and obvious. Worse yet, mas is lecturing to us,

with condescension, for no reason. Only a few of us use EQ or

tone controls in the home. I DO use them in my amateur sound

reinforcement work, to good advantage, but I recognize the results may

not be as beneficial at all points in the auditorium.

When you mud wrestle with a pig, you both get dirty but the pig likes it!

When you two can find time to climb out of the mud and take a break from your mutual admiration society grope fest, you might want to take a gander at pages 329 to 422 of Sound System Engineering, 3rd Edition. And I am glad you are enjoying the typo! Shawn devotes an entire entry to it as the myriad other references in far too many threads are not enough to indicate that it is an obvious typo. But then a basic understanding of the issue would have rendered that point moot. Especially as he is still upset that his model is only valid in a minimum phase environments and is a prime example of the fundamental limitation of EQ, and not the panacea for the majority of environments that he had initially imagined..

Heck, even Wikipedia has an entry defining 'minimum phase', although you will want to look under the 'continuous time-frequency analysis' entry...which granted focuses on the electrical perspective. You know, the one that someone so adroit with filter analysis and EQ should already be familiar ...

Yup, you might discover that this is a very real consideration and fundamental limit in both electronic design and acoustics. But then for some, EQ is simply a 'tone control'.

If you want to think of minimum phase as being a system where the component signals are synchronized in time, you can. It is more complex than that, and you can view it from an electrical or an acoustical perspective. And for starters, how comfortable are you at analyzing LaPlace transforms and S Plane diagrams, or evaluating frequency-phase diagrams in the form of Nyquist spirals? You might just have to revise your limited POV.

But I rather enjoy your personal attacks, albeit it they are not very creative, especially coming from one whose exposure to science IS watching an episode of Star Trek. ...yup, maximum phase is 349.327 degrees @ 122Hz.. A departure from the more standard answer of 7. And you know, I don't care if you use tone controls. Heck, I don't even care if you use tubes or SS or if you have exotic interconnects.or listen to wire recordings, 8 track tapes, records or CDs. My concern is elsewhere.

The really hilarious thing is that by denigrating the concept of minimum/non-minimum phase and the people who speak in terms of this aspect, you not only declare your ignorance for all to see, but you are not denigrating me. I am not the originator of the concept. I simply employ it and have tried to introduce such concepts to you learned folks. Nope, in denigrating the concept, you simply demonstrate rather conclusively that you haven't a clue, and you you are attacking a great many people who know more than either of us. The only real difference is that I know this and you do not. Well, that and the fact that I don't run to Amy when someone offers personal attacks like so many others here do. But not to worry, I will try to include some nice pictures, as I know how that makes some very happy.

But what ever you do... Don't attempt to find out where and when EQ is appropriate to be used and when it is not. I, unfortunately, have heard far too many of such SR systems. That's just another benefit of carrying earplugs.

By the way, most of this issue (and what is in the SSE) was initially presented by Dr. Gene Patronis and Don Keele at the Loudspeaker Design Seminar in Atlanta in February 1991 (if my memory recalls the date correctly). I'm sorry if my sources aren't quite as smart as you John, but gee, they sure had lots of pretty pictures, so it managed to keep most of us happy. Ironically Klipsch had representatives in attendance as well.

[mark1101]

If anyone likes, I can post some measured comparisons of quite a few of the currently available DSP.units. You will note quite a discrepancy among the various units.

Mas,

I would like. Thanks

[mas]

If anyone likes, I can post some measured comparisons of quite a few of the currently available DSP.units. You will note quite a discrepancy among the various units.

Mas,

I would like. Thanks

You are welcome.

nl053_dsp_comparison_part1.c2.pdf

[mas]

and

nl054_dsp_comparison_2.pdf

[pauln]

Anyone else suspect that MAS does not type his posts but actually dictates them into a system that converts voice to text?

And that the EQ settings on that converter need to be adjusted?

[mas]

Anyone else suspect that MAS does not type his posts but actually dictates them into a system that converts voice to text?

And that the EQ settings on that converter need to be adjusted?

I'll try playing with the pitch adjustment, as I speak v e r y slowly just for you.

[Travis In Austin]

I'm with Coyotee-O on this, what in the heck does all of this mean in lay terms. Does it mean you should not use EQ even if it sound better? Does it mean if EQ sounds better you are an idiot. Does it mean that people who make EQ's are in a conpiracy with the people who make audio cables? Or, does it mean that if you don't have an EQ you are missing out on a lot of stuff? Or does it mean that if you had an EQ you could be listening a whole lot better?

Travis... I'm beginning to think that there is a conspiracy and it really means those who make the planes are in cahoots with those who make the conveyor belts....thereby forcing us all to buy automobiles since our personal planes are confused about whether or not they'd take off.....

[ap]..............

[au]..............

[:^)]

You got it half right, the conveyor belt people are in cahoots with the airplane wheel manufacturers, and those folks consipire to compromise the quality of raw PVC that is required for the making of LP's, and as a result, the PVC folks are pumping more oxygen into copper which requires people to buy expensive cables. I have not chased it down completly, but I am on the right track, I know it.

[bodcaw boy]

Hungarian Proverb: It is not enough to be impolite, you must be wrong, too.

i love that!!

have a blessed night,

roy

[johnyholiday]

OMG ribbon graphs pretty!! ........"over an out" on the zinky superfly walkie talkie

[pauln]

Hungarian Proverb: It is not enough to be impolite, you must be wrong, too.

i love that!!

have a blessed night,

roy

Hi Roy!

I like it too... sort of says it all, doesn't it?

I actually was fortunate enough to spend some time in Hungary a few years ago. It is very beautiful and the people are facinating - European in culture, but unspoiled in the modern Western sense. One of the first nights there I went out looking for dinner and found a pizza place. As they cooked it they asked if I wanted tomato sauce. Answering "yes" I was surprized when they served it with a bowl of tomato sauce on the side... The next night I decided to try local dishes. The most popular one is a bowl of soft peices of beef and liquid with a 1/2 inch layer of liquid grease on the top served with a basket of bread. It is quite good. Each peice of meat gets a tasty thin coating of grease as you fork it out of the bowl. When you are finished all that is left is a bowl of grease. For me, that was the end of the meal, but for the real Hungarians they dip the bread in the grease and finish it all up.

Darn, it's almost 2:30AM and now I'm hungy.

Have a blessed tomorrow!

Pauln

[mike stehr]

http://profile.myspace.com/index.cfm?fuseaction=user.viewprofile&friendid=29457277